Wireless power supply is a convenient and safe new technology through which electrical energy can be transferred to a load wirelessly without any physical connections, and within a close distance. As compared with conventional power supplies, a wireless power supply structure can provide several advantages, such as being frictionless to be easily maintained due to the non-contact between the power supply system and the load, noiseless and free from pollution due to the non-limit by the speed of the load, adaption to various poor conditions (e.g., underwater, snow and ice weather, underground, etc.), and lower volume due to the higher operation frequency. Wireless power supplies have been applied in battery charging fields, and to drive a single load.